Johannesburg - Vodacom Group, the largest provider of mobile-phone services in South Africa, is set for its biggest decline in more than 16 months after third quarter domestic revenue contracted.

The stock retreated as much as 5.7 percent and traded 5.4 percent down, the biggest intraday retreat since September 2011, to 114.80 rand by 3:02 p.m. in Johannesburg trading.

A close at this level will be the lowest since November 9, according to data compiled by Bloomberg.

Volume traded was 2 1/2 times the three-month daily average.

Revenue from mobile voice, accounting for about half of domestic receipts, fell 2.3 percent to 7.6 billion rand ($850 million) for the three months through December, the company said today.

Contribution from mobile messaging contracted 5.6 percent to 777 million rand.

“It’s a warning sign, a negative indicator, for mobile pricing going forward because of competition and aggressive promotion,” said Kate Turner-Smith, sub-Saharan Africa research analyst at Cape Town-based BPI Capital Africa, in a phone interview today. “The results weren’t bad enough to warrant such a decline.”

The number of active customers rose about 12 percent to 30.6 million in the quarter compared to a year earlier, the company said. Total revenue grew 1.7 percent to 18.3 billion rand.

UK-based Vodafone Group Plc owns 65 percent in Vodacom, data compiled by Bloomberg show. - Bloomberg